What is Autonomous Emergency Braking and can we trust it?

A bold statement, but many road safety experts are convinced Autonomous Emergency Braking, or AEB, is that significant in reducing road deaths and injuries.

So what is it? As the name suggests, the car will take charge of emergency braking if it detects an accident is imminent and the driver hasn't responded quickly enough.

AEB is typically the next stage after a car's forward collision detection system has issued the driver a warning (an alarm in the cabin and warning light flashing); automatically and forcefully (if required) applying the brakes to prevent an accident or at the very least dramatically lower the speed of an impact.

Autonomous Emergency Braking systems use radars, cameras or sensors to detect hazards and brake for you if necessary

In the real world, that may be if an animal runs in front of your car, you've not noticed a merging or slowing car in front of you, or - and this is an ever-increasing problem - drivers are distracted by illegally using their phones when behind the wheel.

Looking down while texting and driving and the car in front stops? AEB may well slam your brakes on, prevent a collision and remind you you're being an idiot.

Cars with AEB use radar, laser or cameras (or a combination of these) to intelligently analyse risk of impact with another vehicle or pedestrian for example.

Some work only at lower speeds - say up to 50kmh - but increasingly AEB is improving at such a pace that it can be effective up to very high speeds - BMWs with Driving Assistant Plus can work up to an incredible 210kmh.

But does it work properly in the real world? All new technologies need fair time to evolve and improve, and from personal experience I've had two contrasting episodes with AEB on my Skoda Fabia: a sub $20k car which impressively has AEB as standard (they call it Skoda Front Assistant).

Autonomous Emergency Braking systems use radars, cameras or sensors to detect hazards and brake for you if necessary

A taxi recklessly pulled out in front of our car in slow moving traffic while my wife was looking for a parking space on the other side of the road. She hadn't seen the now braking taxi, and the Skoda beeped then braked in almost the blink of an eye. Low speed bump happily avoided.

Not so good was my recent experience. A large paper bag flew in front of the Skoda while I was driving in town at about 50kmh. The radar clearly sensed a solid object in its path, it knew a collision was imminent, but it of course didn't know it was a harmless bit of paper I'd be happy to hit.

For all the Skoda's AEB system knew it was a solid metal car and it had to try to stop.

With no warning the brakes slammed on - I thought the engine had abruptly seized - and we came to a complete stop. As the bag harmlessly flew on its journey the car seemed to realise its "error" and released the brake.

I was caught in two minds after this incident. On the one hand I was impressed at how the system had worked so effectively and quickly, and had said paper bag been a child running in front of the car the impact would have been lessened markedly.

But it was a paper bag; something harmless that would have been fine to hit at any speed. As a result, I would have been mightily unimpressed if a non-AEB car or even truck had been behind me and slammed into the back of my car as I seemingly made an emergency stop for no reason.

This personal experience has highlighted to me how imperfect some autonomous systems are.

I know most will be for the greater good, but we must also accept there will be limitations, and as in my case, a potential accident caused by AEB too.

Autonomous Emergency Braking systems use radars, cameras or sensors to detect hazards and brake for you if necessary